Lathe

ABSTRACT

A lathe ( 10 ) having a lathe bed ( 11 ) on which is mounted a cutting station at which a cutting tool ( 13 ) can be mounted, a guide defining a guide path for guiding relative feeding movement between a workpiece holder ( 14 ) and the cutting tool ( 13 ), and drive means ( 15 ) for relatively moving the workpiece and the cutting tool ( 13 ) to engagement with each other. In order to provide a gap-swing facility, and avoid present requirement in known lathes to provide a “removable gap-piece”, the invention provides a guide in the form of three parallel guide elements, namely a main front guide-way ( 17 ), a tailstock bed-way ( 18 ) and a rear ante-roll guide-way ( 19 ), which are spaced apart from each other and relative to the centre line ( 16 ) of the workpiece holder ( 14 ). The three parallel guide elements in the invention provide a permanent gap or cavity in the lathe bed structure ( 11 ), to provide the required gap-swing facility and substantially without loss of guide-way support.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/806,382, filed Aug. 15, 2001, which claims priority toUnited Kingdom Application No. 9918623.1, filed Aug. 9, 1999, whichapplications are incorporated herein by specific reference.

BACKGROUND OF THE INVENTION

[0002] 1. The Field of the Invention

[0003] This invention relates to a lathe having a lathe bed, a cuttingstation provided on the lathe bed and at which a cutting tool can bemounted, a guide mounted on the lathe bed and defining a guide path forguiding relative movement between a workpiece and the cutting tool, anddrive means for relatively moving the workpiece and the cutting tool toengagement with each other.

[0004] 2. The Relevant Technology

[0005] In known designs of lathe, it is usual to provide a so-called“removable gap-piece”, and which (when removed) temporarily gives anincreased “gap-swing” capacity for a short distance in front of theusual faceplate which holds the workpiece. However, with existingdesigns, the presumed requirement of lathe operators for a removablegap-piece facility presently imposes a number of technical drawbacks,which can include (a) loss of overall accuracy (b) reduction of rigidityand (c) undesirable wear characteristics of the lathe.

BRIEF SUMMARY OF THE INVENTION

[0006] The present invention therefore seeks, in one aspect, to providean improved design of lathe which allows for elimination of atraditional removable gap piece, while at the same time seeking toprovide improved overall accuracy in operation, rigidity and enhancedwear characteristics of the lathe.

[0007] According to one aspect of the invention there is provided alathe having a lathe bed on which is mounted:

[0008] a) a cutting station at which a cutting tool can be mounted;

[0009] b) a guide defining a guide path for guiding relative feedingmovement between a workpiece holder and the cutting tool; and

[0010] c) drive means for relatively moving the workpiece and thecutting tool to engagement with each other:

[0011] in which the guide comprises three parallel guide elements whichare spaced apart from each other and relative to the centre line of theworkpiece holder such that a permanent gap or cavity is defined in thelathe bed structure to provide a gap-swing facility and substantiallywithout loss of guide-way support.

[0012] Preferably, the three parallel guide elements comprise a mainfront guideway, a tailstock bed-way, and a rear anti-roll guideway.

[0013] The drive means may take the form of a usual lead screwarrangement.

[0014] The cutting tool is preferably carried by a travelling assemblymovable along the guide elements, and including two front carriagesslidable along the main front guideway, and a further carriage unitslidable along the rear anti-roll guideway.

[0015] The preferred provision of a three-point linear guidewayconfiguration (two carriages slidable along the front main guideway andone preferably less heavily pre-loaded carriage unit sliding on the rearanti-roll guideway) allows for some geometric mis-alignment, thusfurther improving overall slide-way accuracy.

[0016] The geometry of the arrangement of the guide elements, inrelation to the centre line of the workpiece holder (main spindle centreline) is arranged, as indicated above, to provide a permanent cavity orgap in the lathe bed, and to allow for appropriate extra “gap-swing”which may be required, without the usual loss of slide-way support whichnaturally occurs when a traditional gap piece is removed in knowndesigns of lathe provided with this facility.

[0017] Further advantages of the embodiment of the invention are thatthe loss of accuracy, often introduced by non-perfect refitting of atraditional gap piece (after removal for “swing-in gap work”) iseliminated. In addition, the length limit imposed by a gap piece (to thedesirably long and narrow) main guideway may also be eliminated, thusgiving opportunity to increase this length and consequently provideimproved slideway accuracy, rigidity and enhanced wear properties.

[0018] According to a further aspect of the invention there is provideda lathe having a lathe bed on which is mounted:

[0019] a) a cutting station at which a cutting tool can be mounted;

[0020] b) a guide defining a guide path for guiding feeding movement ofthe cutting tool relative to a workpiece holder; and

[0021] c) drive means for advancing the cutting tool into engagementwith a workpiece when mounted on said holder;

[0022] in which the lathe excludes provision of a removable gap piece,and in which said guide comprises three parallel guide elements whichare spaced apart from each other and relative to the centre line of theworkpiece holder that a permanent gap or cavity is defined in the lathebed to provide a gap-swing facility and substantially without loss ofguide-way support for the movement of the cutting tool.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] A preferred embodiment of lathe according to the invention willnow be described in detail, by way of example only, with reference tothe accompanying drawings, in which:

[0024]FIG. 1 is a plan view of part of the lathe according to theinvention;

[0025]FIG. 2 is a front view of the part of the lathe shown in FIG. 1;and

[0026]FIG. 3 is an end view and taken on sectional line X-X in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Referring now to the drawing, there is shown a preferredembodiment of lathe according to the invention, and which eliminatesprovision of traditional removable “gap-piece”. A gap-piece istraditionally provided in existing designs of lathe, in order toprovide, temporarily, an increased gap-swing capacity for a shortdistance in front of the usual face plate holding a workpiece, whilstthe gap piece is removed.

[0028] The lathe according to the invention excludes requirements forprovision of a removable gap piece, while still providing a gap swingfacility, and while at the same time also giving improved and increasedoverall accuracy, rigidity and wear characteristics to the latheaccording to the invention.

[0029] The lathe is designated generally by reference 10, and includes alathe bed structure 11 on which is mounted a travelling cutting stationassembly 12 which carries cutting tool 13. The bed 11 also mounts aguide which defines a guide path for guiding relative feeding movementbetween a workpiece (not shown) carried by workpiece holder 14 and thecutting tool 13. There is also provided drive means for relativelymoving the workpiece and the cutting tool to engagement with each other,and which takes the form of a lead screw arrangement 15.

[0030] The travelling cutting station assembly 12 is slidable alongthree parallel guide elements, which constitute the tool guide, andwhich are spaced apart from each other, and also relative to the centreline 16 of the workpiece holder 14, which comprises usual main spindlecentre line.

[0031] The three parallel guide elements which make up the tool guidecomprise a main front guideway 17, a tailstock bed-way 18 and a rearanti-roll guideway 19.

[0032] By virtue of the geometry of the arrangement of the threeparallel guide elements, both in relation to each other, and alsorelative to the centre line 16 of the workpiece holder, a permanent gapor cavity can be defined in the lathe bed structure 11 to provide aguide-swing facility, and substantially without loss of slideway (guideway) support.

[0033] The cutting tool 13 is carried by travelling assembly 12 which isslidable along the guide elements, and comprises two front carriages 21and 22 which are slidable along the main front guideway 17, which is along narrow front guideway.

[0034] The travelling assembly 12 also includes a less heavilypre-loaded carriage unit 23 which is slidable along the rear anti-rollguideway 19.

[0035] Therefore, in the embodiment of lathe 10 according to theinvention, a gap swing facility is provided, despite the absence of thetraditional arrangement of removable gap piece. This is achievedsubstantially without loss of slideway support, which normally occurswhen a traditional removable gap piece feature is provided, and uponremoval.

[0036] Furthermore, the embodiment of the invention can avoid the lossof accuracy, which is often introduced by non-perfect refitting of atraditional gap piece, after removal for “swing-in gap work”. Inaddition, the length limit imposed by a traditional removable gap piece(to the desirably long and narrow) main guideway is also eliminated,thus giving opportunity to increase this length and consequently provideimproved slideway accuracy, rigidity and enhanced wear resistantproperties.

[0037] The three point linear guideway configuration (the carriages 21and 22 on the front main guide way 17 and the preferably less heavilypre-loaded carriage unit 23 sliding on the rear anti-roll guideway 19)allows for some geometric mis-alignment, thus further improving overallslideway accuracy. Furthermore, the low position of the main guide way17 relative to the spindle centre line 16, together with the positioningof the lead screw 15 (near the main guideway 17, but between the mainguideway 17 and rear guideway 19) causes major cutting forces to beabsorbed directly into the main guideway 17, thus promoting maximum loadcapacity and further enhancing long term accuracy, rigidity and wearresistant characteristics.

What is claimed is:
 1. A lathe comprising a lathe bed on which ismounted: a cutting tool; a workpiece holder adapted to hold a workpiece;a guide defining a guide path for guiding relative feeding movementbetween the workpiece holder and the cutting tool, the guide comprisinga front guide-way, a tailstock bed-way, and a rear guide-way whichextend parallel to each other; and drive means for relatively moving theworkpiece holder and the cutting tool so that the cutting tool canengage the workpiece when mounted on the workpiece holder, the frontguide-way extending lengthwise of the lathe bed towards the workpieceholder and beyond the ends of the tailstock bedway and the rearguide-way so as to define a permanent gap or cavity in the lathe bed andthereby provide a gap swing facility without requirement for a removablegap piece and substantially without loss of guide-way support.
 2. Alathe according to claim 1, in which the cutting tool is carried by atraveling assembly which is movable along the guide, the travelingassembly including a first carriage and a second carriage which areslidable along the front guide-way, and a further carriage which isslidable along the rear guide-way.
 3. A lathe according to claim 2, inwhich the first carriage is selectively movable on the front guide-wayto a position substantially below the workpiece holder.
 4. A latheaccording to claim 2, in which the drive means comprises a lead screwarrangement which is operative to move the traveling assembly towardsthe workpiece holder.
 5. A lathe according to claim 4, in which thefront guide-way is located a sufficient distance below a center line ofthe workpiece holder, and the lead screw arrangement is arranged near tothe front guide-way and between the front guide-way and the rearguide-way so as to provide a lathe guide geometry which causes the majorcutting forces to be absorbed directly into the front guide-way.
 6. Alathe according to claim 1, in which the rear guide-way is an anti-rollguide-way.